C++ :: Initializing A Class To A Pointer?

I came across a piece of c++ code that seems to be initializing a class object like this:

ImapMailbox *mailbox;

Now the class looks like this:

class ImapMailbox {
public:
ImapMailbox();
ImapMailbox (const QString& mailbox);
~ImapMailbox();
// Methods
void addMessage (ImapMessage *message);

[Code]...

And the constructor looks like this:

ImapMailbox::ImapMailbox()
: d(new ImapMailboxPrivate)
{
d->unseen = d->exists = d->recent = 0;
d->readWrite = false;
d->flags = 0;
}

But this does not seem to be an array like object. So what exactly could this be pointing to?